Stephen was a young prominent member of the early Christian church who served as a deacon in the church of Jerusalem. He was eventually accused of blasphemy by the Sanhedrin, and consequently after giving a detailed speech about the history of Israel, and how Jesus was the Messiah, he was stoned to death by a crowd stirred up by Saul and would become the first Christian martyr. 
Appointed as Deacon
During the rise of the early Church, the Apostles grew worried about negligence in the daily distribution of food, due to complaints from Hellenistic Jews. So they gathered the disciples in Jerusalem, telling them to appoint seven men whom that responsability would be delegated. Stephen was one of the chosen, and he was noted as being "full of faith and of the Holy Spirit" . Stephen was presented to the Apostles, who laid their hands on him while praying and sending him on his appointment.
Arrest and Trial
Stephen faced opposition from religious leaders belonging to the Synagogue of the Freedmen. However, each time they confronted him, Stephen answered while empowered with the Spirit, and they couldn't stand up to him.  So they decided to stir the people up, falsely accusing Stephen of blasphemy. The elders and the teachers of the law were notified of this, and Caiaphas ordered Stephen to be arrested and brought before the Sanhedrin.
False witnesses were also brought to Stephen's trial, claiming that he spoke heresies against the Law of Moses and said that Jesus will destroy the Temple.  Now, when the members of the Council looked up to Stephen, they noted his face looked like that of an angel.  Caiaphas asked Stephen if he assumed the charges. Stephen answered with a lengthy speech, narrating the history of the Hebrews since the days of Abraham. He condemned the members of the Council, confronting them because of their obstinacy and resisting the Holy Spirit. He also compared them to whose who persecuted and killed prophets, and blamed them of the death of Jesus Christ. 
The members of the Sanhedrin were enraged and threatened Stephen, who, looking up to the heavens, saw the glory of God, and Jesus at his right side. When Stephen described his vision to the Councilors, they covered their ears and yelled in disbelief and anger. In a fit of rage, the religious leaders grabbed Stephen and dragged him out of Jerusalem. 
Death and Legacy
Stephen was then subjected to stoning by the Councilors and the crowd of false witnesses. While being hit by the rocks, Stephen prayed to God, and also forgave his persecutors before dying. Stephen was the first Christian to give his life because of Jesus, becoming the first of many martyrs. 
Saul of Tarsus witnessed Stephen's death, having been left in charge of the crowd's coats during the execution. That day, the conservative Jews began a great persecution to the Early Church in Jerusalem, whose members were scattered through Judea and Samaria. Some members of the church buried Stephen and mourned for him. 
Stephen's martyrdom was not in vain: the scattering of the Christian faith meant the good news of Jesus's coming were spread to many places , and even reached non-Jews, such as Romans and Samaritans, thanks to Peter  and Stephen's former partner Philip . Saul's commitment to persecute the Church, fueled by his approval of Stephen's death, ended with him personally facing Jesus, converting to Christianity, and becoming the greatest missionary of his time.